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RIVERS

RIVERS. EROSIONAL PROCESSES By Gary Thomas. Objectives:. Students should be able to: Define river erosion Name the four processes of river erosion Explain, using diagrams the processes of river erosion. What is river erosion?.

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RIVERS

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  1. RIVERS EROSIONAL PROCESSES By Gary Thomas

  2. Objectives: Students should be able to: • Define river erosion • Name the four processes of river erosion • Explain, using diagrams the processes of river erosion

  3. What is river erosion? This is the wearing away and removal of rock, soil and minerals from the bed and banks of a river.

  4. Erosional Processes Rivers erode their bed and banks in four main ways: • Hydraulic Action • Corrosion or Solution • Corrasion or abrasion • Attrition

  5. Hydraulic Action • The breaking down of rocks • Removing and dragging rocks from the bed and banks of the river by the force of the running water (like a water jet) • Usually there are lines of weakness like joints and cracks in the river • The work of hydraulic action forms plunge pools (small lakes)

  6. Corrosion or Solution • The solvent action of water dissolves soluble materials and carry them away in solution • The river water acts as a solvent and dissolves soluble minerals such as limestone. The presence of carbon dioxide would help to dissolve limestone (calcium carbonate) faster due to the chemical reaction between them.

  7. Corrasion or Abrasion • The river uses its load to grind against the bed and sides • The action would dislodge the materials and carry them away • This process operates in 2 ways (vertical--> depth; lateral--> width) • Potholes are the product of corrasion

  8. Attrition • The loosened materials that are being carried away collide against the river sides and bed and against one another • Over time, they would become smaller and eventually reduced to fine particles called silt

  9. Test yourself • 1. What are the four processes of river erosion called? A. erosion; abrasion; traction and solution? B. hydraulic action; attrition; saltation and abrasion? C. abrasion; attrition; hydraulic action and solution? D. traction; suspension; attrition and abrasion? Ans. : C

  10. Test yourself • 2. Which of the following mainly produces potholes? A. Corrosion B. Attrition C. Abrasion D. Hydraulic Action Ans.: C

  11. THE END

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